Laminar scrubber apparatus for capturing carbon dioxide from air and methods of use

ABSTRACT

The present invention is directed to methods for carbon dioxide from air, which comprises exposing solvent covered surfaces to air streams where the airflow is kept laminar, or close to the laminar regime. The invention also provides for an apparatus, which is a laminar scrubber, comprising solvent covered surfaces situated such that they can be exposed to air streams such that the airflow is kept laminar.

CROSS REFERENCE TO PRIOR APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/603,121, filed Aug. 20, 2004 and is incorporated by reference in itsentirety.

This patent disclosure contains material that is subject to copyrightprotection. The copyright owner has no objection to the facsimilereproduction by anyone of the patent document or the patent disclosureas it appears in the U.S. Patent and Trademark Office patent file orrecords, but otherwise reserves any and all copyright rights.

FIELD OF THE INVENTION

The present invention relates generally to the field of extractors,including those that work to extract carbon dioxide. The presentinvention relates to carbon dioxide (CO₂) removal under ambientconditions from the open air without heating or cooling the air.

BACKGROUND OF THE INVENTION

Extracting carbon dioxide from ambient air would make it possible to usecarbon based fuels and deal with the greenhouse gas emissions after thefact. Since CO₂ is neither poisonous nor harmful in parts per millionquantities but creates environmental problems simply by accumulating inthe atmosphere, it is possible to remove carbon dioxide from air inorder to compensate for an equally sized emission elsewhere and atdifferent times. The overall scheme of air capture has been describedelsewhere.

The production of carbon dioxide (CO₂) occurs in a variety of industrialapplications, such as the generation of electricity in by burning coalin power plants. Flue gas from coal-burning power plants typicallycontains a high percentage of nitrogen, about 13% CO₂, about 3% oxygen,about 10% water and less than 1% of various pollutants. To sequester CO₂during the operation of coal burners in power plants, CO₂ must beseparated from the flue gas, which is hot, e.g., temperatures from about200° C. to about 1000° C. depending on its specific locations in theflue gas lines of the coal-burning power plant. In a carbon constrainedworld, central sources of CO₂ like power plants are likely to capturetheir own CO₂ from the power plant stack.

Hydrocarbons are typically the main components of fuels that arecombusted in combustion devices, such as engines. Exhaust gas dischargedfrom such combustion devices contains carbon dioxide gas, which atpresent is simply released to the atmosphere. However, as greenhouse gasconcerns mount, carbon dioxide emissions from all sources will have tobe curtailed.

Scrubber designs for separating CO₂ from air already exist, but they arelimited to packed bed type implementations whose goal is typically toremove all traces of an impurity from another gas. The disadvantages inthe art are addressed and overcome by the carbon dioxide separationmembranes and methods of use thereof as embraced by the presentinvention.

SUMMARY OF THE INVENTION

The present invention is directed to methods for carbon dioxide fromair, which comprises exposing solvent covered surfaces to air streamswhere the airflow is kept laminar, or close to the laminar regime. Theinvention also provides for an apparatus which is a laminar scrubber,comprising solvent covered surfaces situated such that they can beexposed to air streams such that the airflow is kept laminar. Thefollowing descriptions of the invention include many embodiments andaspects, all of which can be attributable to either the method or theapparatus claimed, even if not so explicitly stated.

Capture of carbon dioxide on board of a vehicle while possible inprinciple is not practical because of the large amount of weightinvolved. Therefore our invention aims at capturing carbon dioxide fromthe air at a later time. The purpose of the removal of carbon dioxidefrom the air is to balance out the carbon dioxide emission resultingfrom the operation of vehicle. While the most obvious source of carbondioxide emissions that could be remedied by this invention are those forwhich it would be difficult or impossible to capture the CO₂ at thepoint of emission, the invention is not restricted to such sources butcould compensate for any source as well. Indeed this approach of carbondioxide mitigation could be used to lower the atmospheric concentrationof CO₂.

Efficient capture of carbon dioxide from air requires a sorbent that canabsorb CO₂, processes that heat or cool the air, or that change thepressure of the air by substantial amounts will be energeticallydisadvantaged.

The apparatus consists of a scrubber design which provides essentiallystraight flow paths for the air that is blowing through the device.Sorbent covered surfaces are within millimeters to centimeters of theflow path of every air parcel. The simplest embodiment is a set of flatplates with the air moving through the gaps between the plates and thesorbent flowing over the surfaces. In the simplest design these platesstand upright so that wetting of both surfaces can be performed withequal ease. However a variety of other designs describe below can varyfrom this simple design. These include but are not limited to corrugatedsurfaces, concentric tubes etc.

In one aspect of the invention, the surfaces are smooth parallel plates.In another aspect, the surfaces are not entirely flat, but followstraight parallel lines in the direction of the airflow. Examplesinclude but are not limited to corrugations, pipes or tubes, angularshapes akin to harmonica covers. The invention provides for methodswhere the surfaces are roughened with grooves, dimples, bumps or othersmall structures that are smaller than the surface spacing and thatremain well within the laminar boundary of the air flow, i.e., theReynolds number of the flow around these dimples is small, in an optimumit is between 0 and 100.

The present invention is directed to implementations of the above methodwhere surface roughening has been obtained through sand blasting orother similar means. In one aspect of the invention, the surfaceroughening can be obtained by etching.

In another aspect of the invention, the apparatus contains surfaces thatare part of plates made from steel or other hydroxide resistant metals.In one aspect of the invention, the plates are made from glass. Inanother aspect, the plates are made from plastics, including but notlimited to polypropylene.

In yet another aspect of the invention, the surfaces are foils or otherthin films that are held taught by wires and supported by taught wire orwire netting. The invention provides for an apparatus where all but asupporting wire in the front and the back run parallel to the wind flowdirection. In one aspect, the films are supported on a rigid structure.For example, the rigid structure can be a solid plate, a honeycomb, orlatticework that can lend structural rigidity to the films. Theinvention is not limited to these examples.

The invention also provides for an apparatus and method where the filmsare made from plastic foils. The invention provides for an apparatus andmethod where the plastic foil has been surface treated to increase thehydrophilicity of the surface. Such treatments can be state of the artor represent novel treatments. In another aspect of the invention, anapparatus or method is provided where surfaces have been coated ortreated to increase hydrophilicity of the plates.

The method or apparatus of the invention further provides that thedirection of the airflow is horizontal. The method or apparatus of theinvention provides that the the surfaces—or the line of symmetry of thesurfaces—is vertical. The invention provides for where the liquidsolvent flow is at right angle to the airflow. The invention providesfor a method and an apparatus where the surface spacing is between 0.3centimeters (cm) and 3 cm. In another embodiment, the surface length atright angle to the airflow direction is between 0.30 m to 10 m. Inanother embodiment, the airflow speed is between 0.1 meters per second(m/s) and 10 m/s. In another embodiment, the distance of airflow betweenthe surfaces is between 0.10 m and 2 m.

In one embodiment of the invention, liquid solvent is applied by meansof spraying a flow onto the upper edge of the surface. In anotherembodiment, the solvent is applied to both sides of the plates. Inanother embodiment, the solvent is applied in a pulsed manner. Inanother embodiment, the liquid solvent is collected at the bottom of thesurfaces or plates in a catch tray.

In another embodiment of the method and apparatus, the collected fluidor CO₂ solvent is immediately passed on to a recovery unit. In anotherembodiment, the collected fluid is recycled to the top of the scrubbingunit for additional CO₂ collection.

In another embodiment of the method or apparatus of the invention, theapparatus is equipped with airflow straighteners to minimize losses frommisalignment between the surfaces and the instantaneous wind field.

In another embodiment of the method or apparatus of the invention, theapparatus is equipped with mechanisms that either passively or activelysteer the surfaces so that they point into the wind.

In another embodiment of the method or apparatus of the invention, thelaminar wind scrubber utilizes pressure drops created by naturalairflows. In one embodiment, the pressure drops created by naturalairflows include, but are not limited to: (a) wind stagnation in frontof scrubber; (b) pressure drops created by flows parallel to theentrance and/or exit into the scrubbers; (c) pressure drops created bythermal convection as for example in a cooling tower or by thermalconvection along a hill side.

In one embodiment of the method or apparatus, the surfaces are rotatingdisks where wetting is helped by the rotary motion of the disks, and theair is moving at right angle to the axis. In one embodiment of themethod or apparatus, the axis is approximately horizontal and the disksdip into the solvent at their rim and the circular motion promotesdistribution of the fluid on the disks.

In another embodiment, the liquid is sprayed onto the disk as it move bya radially aligned injector. In another embodiment, the liquid isextruded onto the disk near the axis.

In another embodiment of the invention, the surfaces are concentrictubes of circular or other cross-section shape with the air flowing inthe direction of the tube axis. In another embodiment, the tubes rotatearound the center axis. In one embodiment of the invention, the tubeaxis is oriented approximately vertically and solvent is applied in amanner that it flows downward on the surfaces of the tube. In anotherembodiment, the axis is at some angle to the vertical and the solvent isinserted at a single point at the upper opening and flows downward in aspiral motion covering the entire surface.

In one embodiment of the invention, the solvent used in the apparatusand in the method is a hydroxide solution. In one aspect, the hydroxideconcentration is from about 0.1 molar to about 20 molar. In anotherembodiment, the hydroxide concentration is from about 1 molar to about 3molar. In one embodiment, the concentration of the solution exceeds 3molar. In another aspect of the invention, the concentration of thesolution has been adjusted to minimize water losses or water gains. Inanother embodiment of the invention, the concentration of the solutionis allowed to adjust itself until its vapor pressure matches that of theambient air.

In one embodiment, the hydroxide is sodium hydroxide. In anotherembodiment, the hydroxide is potassium hydroxide. In another embodiment,the solvent is a hydroxide solution where additives or surfactants havebeen added. In a further embodiment, the addititives or surfactants workto increase the reaction kinetics of CO₂ with the solution. Withoutlimitation, such addititives could be state of the art or improvementson the art. In one embodiment, the additives are intended to reduce thewater vapor pressure over the solution. Such additives could be state ofthe art or improvements on the art. In a further embodiment of theinvention, the additives or surfactants change the viscosity or otherrheological properties of the solvent. In one aspect of the invention,the additives or surfactants improve the absorption properties of thesolvent to scrub gases other than CO₂ from the air (e.g. ozone). Inanother embodiment, the method or apparatus combines additives thatcreate all or part of the properties disclosed hereinabove.

Additional aspects, features and advantages afforded by the presentinvention will be apparent from the detailed description andexemplification hereinbelow.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to methods and devices to capturecarbon dioxide by absorption into a strongly alkaline solution. Althoughgeneral for sorbent recovery already exist, the present inventioninclude an apparatus designed to expose alkaline fluids to atmosphericair where these fluids absorb CO₂.

An apparatus that performs this task is the first in a series of modulesthat together provide air capture capabilities. The system discussedhere differs from previous CO₂ scrubber designs in that it is optimizedfor capturing carbon dioxide from air rather than scrubbing air clean ofCO₂. As a result uniform extraction from the air or maximum reduction ofthe CO₂ content of the air are not at issue, what matters is maximizingthe rate of CO₂ uptake by the sorbent fluid.

Such technology would provide the ability of delivering gasoline, dieselor other carbonaceous fuels that are effectively carbon neutral becausealready prior to their combustion and amount of CO₂ has been removedfrom the air that matches their ultimate emission. Similarly it ispossible to compensate for the emissions of a car or any other vehicleincluding airplanes by removing the amount of CO₂ that will be emittedover the lifetime of the vehicle before or shortly after theirintroduction to the market.

One Embodiment—Description of an Air Scrubber Unit

The purpose of an air scrubber unit is to remove CO₂ from an airflowthat is maintained by a low-pressure gradient. Air scrubber units couldalso capture other gases present in the air. Typical pressure gradientsare such that they could be generated by natural airflows. Pressuredrops across the unit range from nearly zero pressure to a few hundredsof Pascal, a preferred range is from 1 to 30 Pa and an optimal range maybe from 3 to 20 Pa. However, we explicitly state that we do not limitour claim to units that are exclusively wind driven. We also considerthe use of fans either with or without ductwork to guide the air and weexplicitly consider units that are driven by convection.

Flow velocities through the scrubber unit may range from virtuallystagnant to a few tens of meters per second. A preferred range would befrom 0.5 to 15 m/s an optimal range for wind driven systems ranges from1 m/sec to 6 m/sec.

The apparatus of the invention in one embodiment comprises a flat,hydroxide coated, surfaces approximately centimeters apart. These largeflat sheets are referred to as lamellae. In one embodiment, a singlelamella is bound by two sheets covered in hydroxide solution. Air flowsbetween the sheets and parallel to their surfaces. A set of lamellaethat form a complete and independent unit, which is referred to hereinas a scrubber cell. The typical depths of these surfaces or lamellaerange from tens of centimeters to a few meter and the height can varyfrom tens of centimeter to many meters.

The surfaces could be made from solid plates, light-weight mesh likestructures covered with thin membranes or films, or from thin films thatare held in place with wire mesh structure.

There is quite some flexibility in the overall design, but the followingare important design features that distinguish this approach fromothers:

1) Plate structures are smooth in the direction of the airflow on scalesof the plate separation. (However, incidental or engineered structureson a much finer scale may be used to improve the CO2 transportcoefficient.) Variations in shape that are at right angles to the airflow, are of relatively little concern, as long as they do not interferewith the efficient wetting of the plates, sheets or surfaces.

2) The surfaces are held in place sufficiently tightly or rigidly fortheir flexing or flapping not significantly to reduce pressurevariations between the lamellae.

3) Flow through openings in the surfaces is inhibited so that it cannotsignificantly reduce pressure variations between the lamellae.

4) The spacing between the lamellae is chosen such that the system doesnot transition out of the laminar flow or at least does not deviate muchfrom that regime.

5) The depth of the membrane units is kept short enough to avoid nearlycomplete depletion of the air in the front part of the unit.

6) For utilization of both sides of the plates it is preferable toarrange the surfaces vertically. However, deviations from such a designcould be considered for other flow optimizations.

7) The height of the lamella is chosen to optimize wetting properties ofthe surfaces and to minimize the need for reprocessing the fluidmultiple times.

Applying liquid solvent to the surfaces could follow established stateof the art approaches, e.g. spray nozzles, liquid extrusion. It alsocould be optimized using less conventional approaches. One aspect ofthis invention is directed to one specific approach where the apparatusincludes a laminar flow design that exposes solvent covered surfaces toair streams.

The apparatus of this invention can be designed in various ways so longas it is able to perform the functions described herein. For example,designs could wet vertical surfaces near the top and let gravity run thefluid over the surface until the entire area is covered. Alternatively,the surfaces could be shaped as flat disks get wetted as they rotate.The motion would distribute the liquid along these surfaces.

Examples of designs that are meant as illustration rather than anexhaustive description include

1) flat rectangular surfaces or plates aligned parallel to each other

2) Corrugated surfaces that are lined up parallel to each other

3) Flat disks rotating around a center axis with the air flowing atright angle to the axis of rotation. Liquid could be applied by thewheels dipping into fluid near the bottom of the motion. The standingliquid may only cover the outer rim of the disks or reach all the way tothe axle. Alternatively liquid may be injected onto the rim by liquidwetting near the axle and flowing around the disk due to gravity androtary motion.

4) Concentric tubes or similar shapes where air would be blowing alongthe tube axis.

5) Such tubes could be arranged vertically for counterflow designs withwetting initiated at the upper rim or,

6) nearly horizontally with liquid entering at one end and one point andgetting distributed through a slow rotating motion of the tubes.

Solvents that absorb CO₂ span a wide variety of options. Here we focuson aqueous hydroxide solutions. These would tend to be strong hydroxidesolutions above 0.1 molar and up to the maximum possible level (around20 molar).

Solvents must wet the surfaces of the scrubber. To this end we considervarious means known in the art. These include surface treatments thatincrease hydrophilicity, surfactants in the solvent and other means.

Hydroxides could be of a variety of cations. Sodium hydroxide andpotassium hydroxides are the most obvious, but others including organicsorbents like MEA, DEA etc. are viable possibilities.

Hydroxides need not be pure, they could contain admixtures of othermaterials that are added to change or modify various properties of thesolvent. For example, additives may improve on the reaction kinetics ofthe hydroxide with the CO₂ from the air. Such catalysts could besurfactants or molecules dissolved in the liquid. Additions of organiccompounds like MEA are just one example. Other additives may help inreducing water losses by making the solution more hygroscopic. Yet otheradditives may be used to improve the flow or wettability characteristicof the fluid or help protect the surfaces from the corrosive effects ofthe hydroxide solution.

Wind Collection with Hydroxide Solvents

The rate of uptake of CO₂ into a strong hydroxide solution has been wellstudied [REFS] and we are using the result of these studies to design adevice that will pull CO₂ directly out of a natural wind flown or out ofa flow subject to a similar driving force, e.g. a thermally inducedconvection.

CO₂ uptake into a strong hydroxide solution involves a chemical reactionthat greatly accelerates the dissolution process. The net reaction isCO₂(dissolved)+2OH⁻→CO₃ ⁻⁻+H₂O  (1)

There are several distinct pathways by which this reaction can occur.The two steps that are relevant at high pH areCO₂(dissolved)+OH⁻→HCO₃ ⁻  (2)followed byHCO₃ ⁻+OH⁻→CO₃ ⁻⁻+H₂O  (3)

The latter reaction is known to be very fast, the first reaction on theother hand proceeds at a relatively slow rate. The reaction kinetics forreaction (2) is described by${\frac{\mathbb{d}}{\mathbb{d}t}\lbrack {CO}_{2} \rbrack} = {{\kappa\lbrack {OH}^{-} \rbrack}\lbrack {CO}_{2} \rbrack}$

Hence the time constant describing the reaction kinetics is$\tau = \frac{1}{\kappa\lbrack {OH}^{-} \rbrack}$

The rate constant K has been measured. At 20° C. and infinite dilution,

-   -   κ=5000 liter mol⁻¹s⁻¹=5 m³mol⁻¹s⁻¹

The ionic strength correction is given by

-   -   κ=κ_(∞)10^(0.13A)

At high concentration of CO₂ in the gas, the rate of reaction (2) limitsthe rate of uptake, even though the time constant for a one molarsolution at 0.14 ms is quite short.

Following standard chemical engineering models, e.g. Dankwert orAstarita, one can describe the transfer process in which a gas componentis dissolved or chemically absorbed into a solvent with a standard modelthat combines a gas-side flow transfer coefficient and a liquid sidetransfer coefficient to describe the net flow through the interface. Thetotal flux is given byF=κ _(G)(ρ(x=−∞)−ρ(x=0))=κ_(L)(ρ′(x=0)−ρ′(x=∞))where ρ and ρ′ are the molar concentrations of CO₂ in the gas and in thesolution respectively. The parameter x characterizes the distance fromthe interface. Distances into the gas are counted negative. At theboundary Henry's law applies henceσ′(0)=K _(H)ρ(0)Expressed as a dimensionless factor, K_(H)=0.7¹.¹ Note that typically, Henry's constant has dimensions, asconcentrations on the gas side are measured as partial pressure, i.e.,in units of Pascal or units of atmospheres (atm), whereas the liquidside concentrations are typically measured as moles per liter. Thus atypical unit would be liter/mol/atm.

For the gas side the transfer constant can be estimated as$\kappa_{G} = \frac{D_{G}}{\Lambda}$where A is the the thickness of the laminar sublayer that forms on thesurface of the interface. The thickness of this layer will depend on thegeometry of the flow and on the turbulence in the gas flow. For purposesof this discussion we consider it as given. Our goal is to determine theoptimal choice for A.

For a fluid package, the standard approach to estimating the transfercoefficient assumes a residence time τ_(D) for the parcel on the surfaceof the fluid. This time results from the flow characteristic of thesolvent and it include surface creation and surface destruction as wellas turbulent liquid mixing near the surface.

Since diffusion in the time τ_(D) can mix the dissolved CO₂ into a layerof thickness λ=√{square root over (Dτ_(D))}, the flux from the surfaceis given by $F = {D_{L}\frac{\partial\rho^{\prime}}{\partial x}}$where D_(L) is the diffusion constant of CO₂ and ρ′ the liquid sideconcentration of CO₂. The gradient is evaluated at the surface. Thetransfer coefficient of the liquid is defined from the equationF=κ _(L)(ρ′(x=0)−ρ′(x=∞))

Approximating the gradient by$\frac{\partial\rho}{\partial x} = \frac{{\rho^{\prime}(0)} - {\rho^{\prime}(\infty)}}{\lambda}$shows that for a diffusion driven absorption process$\kappa_{L} = {\frac{D_{L}}{\lambda} = \sqrt{\frac{D_{L}}{\tau_{D}}}}$

Here D_(L) is the diffusion rate of CO₂ in the solvent.

In the presence of a fast chemical reaction where the reaction timeτ_(R)<<τ_(D), the layer that absorbs CO₂ is characterized by thisshorter time, hence the transfer coefficient is given by$\kappa_{L} = \sqrt{\frac{D_{L}}{\tau_{R}}}$

In the presence of a chemical the transfer coefficient is increasedtherefore by a factor $\sqrt{\frac{\tau_{D}}{\tau_{R}}}$

However, this enhancement can only be maintained if the supply ofreactant in the solvent is not limited. In the case of carbon dioxideneutralizing a hydroxide solution, it is possible to deplete thehydroxide in the boundary layer. The layer thickness λ contains an arealdensity of hydroxide ions of ρ_(OH) ⁻ ^(λ) and the rate of depletion is2κ_(L)ρ′_(CO) _(2′) . Thus for the fast reaction limit (eqn. x) toapply,${\frac{\rho_{{OH}^{-}}}{2\rho_{{CO}_{2}}^{\prime}}\frac{\tau_{R}}{\tau_{D}}} ⪡ 1$

In our case, ${\rho_{{OH}^{-}}\tau_{R}} = \frac{1}{\kappa}$

Hence the condition can be rewritten as2ρ′_(CO) ₂ κτ_(D) >I

The critical time for transitioning from fast reaction kinetics toinstantaneous reaction kinetics is approximately 10 sec for ambient airThe transition does not dependent on the hydroxide concentration in thesolution. However, once past the transition, the rate of uptake islimited by the rate at which hydroxide ions can flux to the surface. Itis therefore lower than in the fast limit, and the CO₂ flux is given by$F = {\frac{1}{2}\sqrt{\frac{D_{{OH}^{-}}}{\tau_{D}}}\rho_{{OH}^{-}}}$by forcing F into the form in equation x, we find that$\kappa_{L} = {\sqrt{\frac{D_{{OH}^{-}}}{D_{L}}}\frac{\rho_{{OH}^{-}}}{2\rho_{{CO}_{2}}^{\prime}}}$$\kappa_{L}^{0} = {\sqrt{\frac{D_{{OH}^{-}}}{\tau_{D}}}\frac{\rho_{{OH}^{-}}}{2\rho_{{CO}_{2}}^{\prime}}}$

Here κ_(L) ⁰ is the transfer coeflicient in the absence of chemicalreactions. In the instantaneous regime the flux is independent of theCO₂ concentration in the boundary layer.

The flux can be characterized by an effective transfer coefficient,which can be written asF=κ _(eff)(ρ_(CO) ₂ −ρ′_(CO) ₂ /K _(H))

Here the molar concentrations are for the asymptotic values in the faraway gas and far away liquid In the case of hydroxide solutions, thelatter is zero. Hence, F = κ_(eff)ρ_(CO₂) and$\kappa_{eff} = ( {\frac{1}{\kappa_{G}} + \frac{1}{\kappa_{L}K_{H}}} )^{- 1}$

An optimal design is close to the border between gas side limitation andliquid side limitation. Therefore, we establish a design value for theair side boundary thickness A.$\Lambda \approx \frac{D_{G}}{\sqrt{D_{L}/\tau_{R}}}$

This is approximately 4 mm for air based extraction of CO₂.

These constraints together very much limit a practical design. For a 1molar solution, the total flow has been measured as 6×10⁻⁵ mol m⁻²s⁻¹,which translates into an effective value of 0-4 cm/s which is close tothe theoretical value.

All patent applications, published patent applications, issued andgranted patents, texts, and literature references cited in thisspecification are hereby incorporated herein by reference in theirentirety to more fully describe the state of the art to which thepresent invention pertains.

As various changes can be made in the above methods and compositionswithout departing from the scope and spirit of the invention asdescribed, it is intended that all subject matter contained in the abovedescription, shown in the accompanying drawings, or defined in theappended claims be interpreted as illustrative, and not in a limitingsense.

1. A method for capturing carbon dioxide from air, which comprisesexposing solvent covered surfaces to air streams where the air streamshave a flow that is kept laminar, or close to a laminar regime.
 2. Themethod of claim 1, wherein the surfaces comprise smooth parallel plates.3. The method of claim 1, wherein the surfaces are not entirely flat,and follow straight parallel lines in the direction of the airflow. 4.The method of claim 1, wherein the surfaces comprise corrugations,pipes, tubes, angular shapes akin to harmonica covers, or anycombination thereof.
 5. The method of claim 1, 2, 3 or 4, wherein thesurfaces are roughened with grooves, dimples, bumps or other smallstructures that are smaller than the surface spacing, and wherein thesurface structures remain well within the laminar boundary of the airflow.
 6. The method of claim 5, wherein the Reynolds number of the flowaround these dimples or surface structures is small, in an optimum it isbetween 0 and
 100. 7. The method of any one of claims 1-5, wherein thesurface is roughened through sand blasting or other similar means. 8.The method of any one of claims 1-5, wherein the surface is roughenedthrough etching or other similar means.
 9. The method of any one ofclaims 1-8, wherein the surfaces are on plates made from steel or otherhydroxide resistant metals.
 10. The method of any one of claims 1-9,wherein the surfaces are on plates are made from glass.
 11. The methodof any one of claims 1-10, wherein the surfaces are on plates made fromplastics, including but not limited to polypropylene.
 12. The method ofany one of claims 1-9, wherein the surfaces are foils or other thinfilms that are held taught by wires and supported by taught wire or wirenetting.
 13. The method of claim 12, wherein all but a supporting wirein the front and the back run parallel to the wind flow direction 14.The method of claim 12, wherein the foil or film is supported on a rigidstructure that could be a solid plate, a honeycomb, or lattice work thatcan lend structural rigidity to the films.
 15. The method of claim 12,wherein the films are made from plastic foils.
 16. The method of claim15, wherein the plastic foil has been surface treated to increase thehydrophilicity of the surface.
 17. The method of any one of claims12-16, wherein the surfaces have been coated or treated to increasehydrophilicity of the plates.
 18. The method of any one of claims 1-17,wherein the direction of the air flow is horizontal.
 19. The method ofany one of claims 1-18, wherein the surfaces—or the line of symmetry ofthe surfaces—is vertical.
 20. The method of any one of claims 1-18,wherein the liquid solvent flow is at about a right angle to theairflow.
 21. The method of any one of claims 1-18, wherein the surfacespacing is from about 0.3 cm to about 3 cm.
 22. The method of any one ofclaims 1-18, wherein the surface length is at about a right angle to theairflow direction, which is from about 0.30 m to about 10 m.
 23. Themethod of any one of claims 1-22, wherein the airflow speed is fromabout 0.1 m/s to about 10 m/s.
 24. The method of any one of claims 1-23,wherein the distance of airflow between the surfaces is from about 0.10m to about 2 m.
 25. The method of any one of claims 1-22, wherein liquidsolvent is applied by means of spraying a flow onto the upper edge ofthe surface.
 26. The method of any one of claims 1-22, wherein thesolvent is applied to both sides of the plates
 27. The method of any oneof claims 1-22, wherein the solvent is applied in a pulsed manner 28.The method of any one of claims 1-22, wherein the liquid solvent iscollected at the bottom of the surfaces or plates in a catch tray. 29.The method of claim 28, wherein the collected fluid is immediatelypassed on to a recovery unit.
 30. The method of claim 28, wherein thecollected fluid is recycled to the top of the scrubbing unit foradditional CO₂ collection.
 31. An apparatus or method of any one ofclaims 1-22, wherein the apparatus further comprises and is equippedwith air flow straighteners to minimize losses from misalignment betweenthe surfaces and the instantaneous wind field.
 32. An apparatus ormethod of any one of claims 1-22, wherein the apparatus furthercomprises and is equipped with mechanisms that either passively oractively steer the surfaces so that they point into the wind.
 33. Alaminar wind scrubber that utilizes pressure drops created by naturalair flows comprising: a. wind stagnation in front of the scrubber; b. apressure drop created by flows parallel to the entrance and/or exit intothe scrubbers; or c. a pressure drop created by thermal convection. 34.A scrubber of claim 33, wherein the pressure drop is created in acooling tower or by thermal convection along a hill side.
 35. The methodof claim 1, wherein the surfaces are rotating disks where wetting ishelped by the rotary motion of the disks and the air is moving at rightangle to the axis.
 36. The method of claim 35, wherein the axis isapproximately horizontal and the disks dip into the solvent at their rimand the circular motion promotes distribution of the fluid on the disks.37. The method of claim 35, wherein the liquid is sprayed onto the diskas it move by a radially aligned injector.
 38. The method of claim 35,wherein the liquid is extruded onto the disk near the axis
 39. Themethod of claim 1, wherein the surfaces are concentric tubes of circularor other cross-section shape with the air flowing in the direction ofthe tube asix.
 40. The method of claim 39, wherein the tubes rotatearound the center axis.
 41. The method of claim 39, wherein the tubeaxis is oriented approximately vertically and solvent is applied in amanner that it flows downward on the surfaces of the tube
 42. The methodof claim 41, wherein the axis is at some angle to the vertical and thesolvent is inserted at a single point at the upper opening and flowsdownward in a spiral motion covering the entire surface.
 43. The methodof any one of claims 1-42, wherein the solvent is a hydroxide solution.44. The method of claim 43, wherein the hydroxide concentration isbetween 0.1 and 20 molar.
 45. The method of claim 43, wherein thehydroxide concentration is between 1 and 3 molar.
 46. The method ofclaim 43, wherein the concentration of the solution exceeds 3 molar 47.The method of claim 43, wherein the concentration of the solution hasbeen adjusted to minimize water losses or water gains.
 48. The method ofclaim 43, wherein where the concentration of the solution is allowed toadjust itself until its vapor pressure matches that of the ambient air.49. The method of claim 43, wherein the hydroxide is sodium hydroxide50. The method of claim 43, wherein where the hydroxide is potassiumhydroxide
 51. The method of any one of claims 1-50, wherein the solventis a hydroxide solution where additives or surfactants have been added.52. The method of claim 51, wherein the additives or surfactantsincrease the reaction kinetics of CO₂ with the solution.
 53. The methodof claim 52, wherein the additives reduce the water vapor pressure overthe solution.
 54. The method of claim 52, wherein the additives orsurfactants change the viscosity or other rheological properties of thesolvent.
 55. The method of any one of claims 51-54, wherein theadditives or surfactants improve the absorption properties of thesolvent to scrub gases other than CO₂ from the air.
 56. The method ofclaim 55, wherein additives are combined to create all or part of theproperties recited in claims 52-55.